P1740 First Gear Switch Circuit Malfunction
The P1740 code indicates a malfunction in the first gear switch circuit within the automatic transmission. This code is specific to Chrysler (now Stellantis) vehicles, particularly those with 4-speed transmissions such as the 42RE, 44RE, and 46RE. The first gear switch monitors whether the transmission is actually engaged in first gear and sends this information to the transmission control module (TCM) or powertrain control module (PCM). When the switch signal does not match the solenoid command or is out of range, the code is set.
01. Most Common Causes
- Faulty or misadjusted transmission range sensor (MLP/TRS)
- Damaged or stuck shift solenoid
- Internal transmission wear or hydraulic pressure issues
- Damaged, corroded, or loose wiring in the transmission harness
- Faulty TCM or PCM
- Incorrect transmission fluid level or condition
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission stuck in limp mode or fails to shift properly
- Harsh or delayed engagement into first gear
- Poor acceleration or reduced fuel economy
03. Step-by-Step Diagnosis
Scan for codes and verify P1740 is present; check for related codes.
Inspect transmission fluid level and condition; top off or replace if necessary.
Visually inspect wiring and connectors for damage, corrosion, or looseness.
Test the transmission range sensor (MLP/TRS) and adjust or replace if faulty.
Check shift solenoid operation using a scan tool or multimeter.
Perform a transmission pressure test to rule out internal hydraulic issues.
If all else fails, test the TCM/PCM and replace if defective.
1. Frequently Asked Questions
Is it safe to drive?▼
You can drive short distances at low speeds, but the transmission may enter limp mode, limiting performance. Prolonged driving could cause further damage, so it's best to have it diagnosed and repaired promptly.
How much does it cost to fix?▼
Repair costs vary widely depending on the root cause. Simple fixes like fluid change or sensor adjustment may cost $100-$300, while solenoid replacement or internal repairs can range from $500 to $1,500 or more.